Telephone system



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u -FF GR. MM #SamxtW w M KM u 5 w. A RR w W m M. m w W Patented July 30,1940 PATENT OFFICE TELEPHONE SYSTEM Ralph E. King, Short Hills, andOhmer R. Miller, Morristown, N. J., assignors to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkApplication December 1, 1938, Serial No. 243,348

21 Claims.

This invention relates to telephone systems and particularly to systemscomprising toll offices and automatic switching means for completingtoll calls.

It is the object of the invention to minimize the number of manualswitching operations involved in establishing toll connections, toexpedite the completion of such connections, and to more efficiently andreliably effect the transmission of directive and supervisory signals toand through the automatic switching means employed in completing desiredconnections.

One of the features of this invention is a telephone system comprisingtoll ofiices in which automatic switches are provided for routingincoming calls to called toll and local oflices, the talking conductorsof one or more of the trunk and selector circuits constituting a simplexcircuit for controlling the operation of a relay bridged across one endof these talking conductors, supervisory signals being transmitted froma connected outgoing line or trunk to the incoming line over anon-talking conductor other than the usual sleeve or test conductor. Therelay is operated due to an unbalance between the two sides of thesimplex circuit when the outgoing line or trunk to which the connectionis extended is of such a character as to require that the transmissionpads associated with the incoming line be included in the talkingcircuit, If two lines, each provided with transmission pads, areconnected together, the simplex circuit comprising the talkingconductors of the connection is used to control the transmission pads ofboth lines, one relay being bridged across the talking conductors at oneend of the simplex and another relay being bridged across the talkingconductors at the other end of the simplex.

Another feature of the invention is the provision of a non-talkingconductor between an incoming line and a connected outgoing line fortransmitting supervisory signals from' the outgoing line or trunk to theincoming line in combination with the provision of a simplex .circuitover the talking conductors of the connection for transmittingsupervisory signals from the incoming line to the outgoing line ortrunk, and for controlling the short-circuiting of the transmission padsassociated with the incoming line.

Another feature of the invention is a circuit arrangement whereby acalling toll operator, v

;, during the completion of a connection from an incoming line to adesired toll operator or local subscriber under the control of thecalling operators dial, will receive a stop-dialing signal whenever theconnection is extended to a trunk which is not at the time of seizureready to receive dial impulses, and will receive a startdialing signalas soon as dialing may be resumed. According to this feature a tollroute selector is arranged to transmit a stop-dialing signal to acalling operator as soon as the brushes are selectively advanced to agroup in which each of the trunks is connected to an impulse receiver inresponse to seizure of the trunk, the stop-dialing signal beingcontinued by the seized trunk circuit until an impulse receiver isassociated therewith. In a case where the impulses are being transmittedby a register sender, the stop dial signal can-be used to stop thesending of impulses until the stop-dialing signal ends.

According to a further feature, the dial pilot lamp in an operators dialcircuit is arranged to respond to supervisory signals, including astopdialing signal, received by the associated outgoing trunk circuitwhile the dial circuit is connected to the trunk, the disconnection ofthe dial circuit being effected only upon restoration of the dial key.

Another feature of the invention is the provision, in a toll oflicecomprising selector switches for extending connections from incominglines to outgoing trunks, including t1 unks to community dial oflices inwhich impulse responsive apparatus is connected to a trunk as a resultof its seizure, and to lines including ring-down toll lines, ofsupervisory signaling means individual to each selector having accesstosuch trunks and lines for establishing the required signaling andsupervisory circuits depending upon the character 'of a selected line ortrunk.

These and other features of the invention will be further explained byconsidering their application in the telephone system shownschematically in the drawings of this specification. The

'invention is, however, not limited in its application to the systemshown in the drawings and is generally applicable to toll systemscomprising selector switches for establishing connections includinginteroflice trunks.

Referring to the drawings:

Fig. 1 shows a toll operators cord Cl and operators telephone;

Fig. 2 shows a toll operator's position dial circuit PDI; I

Figs. 3 and 4 .show outgoing jacks J I, J2, answeringjacks J3, J4, andan outgoing trunk circuit OT] connected to jack-J l Fig. 5 showsintertoll selectors TS I and'TS3, an interswitch trunk. circuit ISTI andan assoelated auxiliary intertoll selector ASI, an incoming trunkcircuit ITI connected to jack J3 of Fig. 4, an intertoll trunk T3 withits associated composite signaling circuit CS3, two-way trunk circuitTWT3 and outgoing trunk circuit 0T3 connected to jack J2 of Fig. 3;

Fig. 6 shows a composite signaling circuit CSI connecting trunk circuitOTI of Fig. 3 to one end of intertoll trunk TI;

Fig. 6A shows a two-way trunk circuit TWTI connecting trunk circuit OTIof Fig. 3 to the toll route selector T81 of Fig. 5;

Fig. 7 shows a composite signaling circuit CS2 at the other end ofintertoll trunk TI Fig. 7A shows a two-way trunk circuit TWT2;

Fig. 8 shows toll route selector TS2 associated with the two-way trunkcircuit TWT2 of Fig. 7 and toll route selector TS4 associated with thetwo-way trunk circuit TWTQ of Fig. 9;

Fig. 9 shows outgoing Jacks J5 and J6 and an outgoing trunk circuit 0T2connecting jack J5 to the composite signaling circuit CS2 of Fig. 7 andtrunk circuit TWT2 of Fig. 7A; Fig. 9 also shows an outgoing trunkcircuit 0T4 connecting jack J 6 to the associated two-way trunk circuitTWT4 and through the composite signaling circuit CS4 to an intertolltrunk T4;

Fig, 10 shows answering jacks J7 and J8, an incoming trunk circuit IT2connecting jack J1 to a set of terminals in the bank of selector AS2 ofFig. 14;

Fig. 11 shows an interswitch trunk circuit IST2 connected to sets ofterminals in the banks of selectors T82 and T54 of Fig. 8;

Fig. 12 shows an operators position circuit PC2 and a cord circuit C2for connection with jacks J5, J6, J1, J8, J3, Jill, JH and JI2 .of Figs.9, 10, 15 and 16;

Fig. 13 shows a dial circuit DC2 associated with the position circuitPC2 of Fig. 12;

Fig. 14 shows an auxiliary toll route selector AS2 connected to thetrunk circuit IST2 of Fig. 11;

Fig. 15 shows a ring-down toll line circuit EDI and jacks J9 and J l0associated with a ring-down toll line RDL;

Figs. 16 and 17 show a two-way trunk circuit CDTI connecting one end ofa trunk CDT to terminals in the bank of selector AS2 of Fig. 14;

Fig. 18 shows "a two-way trunk circuit CDT2 in a community dial oificeat the other end of trunk CDT, a trunk finder TF and incoming selectorIS, a connector C, a line finder LFI and first selectorSl, and twosubscribers stations A and B; and

Fig. 19 shows the relative position of each of Figs. 1 to 18, inclusive,to form an intertoll dialing system embodying the features of theinvention.

The system represented in the drawings includes a plurality of tolloflices, each of which comprises a toll board with operators positionsand cords for answering calls incoming from local manual or dialofiices, from toll subscribers lines, from community dial omces, or fromother toll offices and for extending an incoming call to a switchingtrunk leading to it called manual or dial local oflice, to a called tollsubscriber's line, to a community dial oflice, or to an intertoll trunk.Ouigoing jacks connect to switching trunks, toll ines, trunks tocommunity dial offices, and intertoll trunks. Answering jacks aredirectly connected to recording trunks, toll subscribers lines, trunksfrom community dial oillces, and intertoll trunks. 'I'oll route selectorand auxiliary toll route selectors are provided for use on callsincoming over intertoll trunks to establish connections with calledtoll, local, or community dial ofi'ices. The operators positions areprovided with dials for use in controlling the operation of incoming andauxiliary toll route selectors in other toll ofiices and for controllingthe operation of selector and connector switches in local or communitydial ofiices. While not shown in the drawings, the operators positionsmay be provided with key-sets in place of dials, in which case sendersare associated with the outgoingv trunks to register the key-setimpulses and control the selectors.

The toll board in one toll office is represented by an operators cord Cland position dial circuit PDI, the outgoing jacks J l and J2 and theanswering jacks J3 and J4. The jack J I, outgoing trunk OTI, two-waytrunk circuit TWTI, incoming toll route selector TSI, and the compositesignaling circuit CSI are all associated with a two-way intertoll trunkTl, the distant end of which terminates in a second toll office. The

jack J2, outgoing trunk circuit 0T3, two-way trunk circuit TWT3,incoming toll route selector TS3 and composite signaling circuit CS3 areall associated with a two-way intertoll trunk T3, the distant end ofwhich terminates in a third toll oflice. The incoming toll routeselectors, such as TSI and T53, have access to auxiliary toll routeselectors. The auxiliary route selectors, such as ASI, have access totoll lines, intertoll trunks, switching trunks leading to the localofiices, trunks leading to community dial ofiices, and to incoming trunkcircuits terminating at a toll operators positions, such for instance,as the trunk circuit ITI connecting to answering jack J3. Interswitchtrunk circuits such as ISTI are associated with auxiliary routeselectors having access to ring-down toll lines or to community dialoflices of the link type, that is, ofiices in which impulse responsiveapparatus is connected to a trunk in response to its seizure at the tolloflice.

The toll board in the second toll ofiice is represented by the operatorscord C2, position circuit PC2, dial circuit D02, and jacks J5 to Jl2,inclusive. The jack J 5, outgoing trunk circuit 0T2, two-way trunkcircuit TWT2, incoming toll route selector TS2, and composite signalingcircuit CS2 are all associated with the intertoll trunk Tl connectingwith the first toll oflice. The jack J 6. outgoing trunk circuit 0T4,two-way trunk circuit TWT4, incoming toll route selector T84 andcomposite signaling circuit CS4 are all associated with an intertolltrunk T4 leading to a fourth toll office. The incoming toll routeselectors T52 and T84 have access to auxiliary toll route selectors. Theauxiliary selectors, such as AS2, have access to tell lines, intertolltrunks, switching trunks leading to local oflices, trunks to communitydial oilices and to incoming trunk circuits such as IT2 connecting toanswering jack J'L. Interswitch trunk circuit IST2 is individual to theauxiliary selector AS2 which has access to both ring-down lines such asRDL and trunks, such as CDT, to community dial ofilces of the link type.

The outgoing trunk circuits OTI and GT2, incoming two-way trunk circuitsTWTI and TWT2, toll route selector circuit TS2, interswitch trunkcircuit IST2, auxiliary toll route selector A82, incoming trunk circuitIT2, ring-down toll line circuit RDI, and community dial oflicetrunkcircults CDTI and CDTZ are all shown in detail. 75

